Differential device and method of assembling the same

ABSTRACT

A differential device includes: a differential gear mechanism; and an integrated differential case housing the mechanism, the differential case including bearing bosses formed integrally on one and other side portions thereof and aligned on a same axis to be rotatably supported by a transmission case; a work window being provided in the differential case; sleeves rotatably supported by the bosses and connected to side gears of the mechanism liquid-tightly. The sleeves can be passed through an inside of the differential case from the window and fitted and inserted to inner peripheries of the bosses, falling-off prevention devices are provided between the sleeves and the bosses, and seal devices for preventing lubricating oil in the differential case from flowing out are provided between the side gears and the sleeves. Accordingly, when drive shafts are removed from the differential device, the oil in the transmission and differential cases does not flow out.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/611,621, filed 2 Feb. 2015, which claims priority under 35 USC § 119based on Japanese patent application No. 2014-018885, filed on 3 Feb.2014. The subject matter of these priority documents are incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improvement of a differential devicecomprising: a differential gear mechanism; and an integrateddifferential case housing the differential gear mechanism, thedifferential case including: first and second bearing bosses formedintegrally on one side portion and other side portion of thedifferential case and aligned on a same axis to be rotatably supportedby a transmission case; a work window for inserting the differentialgear mechanism, the work window being provided in a peripheral wall ofthe differential case; a pair of sleeves being rotatably supported bythe first and second bearing bosses and being connected to a pair ofleft and right side gears of the differential gear mechanism in a liquidtight manner; oil seals being set between outer end portions of thesleeves which protrude from the first and second bearing bosses and thetransmission case; and left and right drive shafts being connected tothe pair of side gears or the sleeves, and the present invention alsorelates to an improvement of a method of assembling the differentialdevice.

2. Description of the Related Art

Such a differential device is known as disclosed in Japanese Patent No.3751488 and Japanese Patent Application Laid-open No. 2013-72524.

In the above-described differential device, separation between the sidegears and the sleeves enables the differential gear mechanism includingthe side gears to be incorporated into the integrated differential casethrough the work window. Moreover, even when the drive shafts areremoved from the differential device during maintenance, lubricating oilin the transmission case and the differential case is prevented fromflowing out. Thus, lubricating oil does not need to be drained everytime the drive shafts are removed, and ease of maintenance is good.

However, in the conventional differential device, after the differentialgear mechanism including the side gears is incorporated into thedifferential case, the sleeves are fitted and inserted into the firstand second bearing bosses from outside and connected to the side gearsby adhesive bonding or special connecting means. Accordingly, it cannotbe said that ease of assembly is good.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedcircumstances, and an object of the present invention is to provide adifferential device which has good ease of assembly and in which evenwhen drive shafts are removed from the differential device, lubricatingoil in a transmission case and a differential case does not flow out andgood ease of maintenance can be ensured, and a method of assembling thesame.

In order to achieve the object, according to a first aspect of thepresent invention, there is provided a differential device comprising: adifferential gear mechanism; and an integrated differential case housingthe differential gear mechanism, the differential case including: firstand second bearing bosses formed integrally on one side portion andother side portion of the differential case and aligned on a same axisto be rotatably supported by a transmission case; a work window forinserting the differential gear mechanism, the work window beingprovided in a peripheral wall of the differential case; and a pair ofsleeves rotatably supported by the first and second bearing bosses andconnected to a pair of left and right side gears of the differentialgear mechanism in a liquid tight manner, wherein oil seals are to be setbetween outer end portions of the sleeves which protrude from the firstand second bearing bosses and the transmission case, and left and rightdrive shafts are to be connected to the pair of side gears or thesleeves, wherein the sleeves are configured to be capable of beingpassed through an inside of the differential case from the work windowand fitted and inserted to inner peripheries of the bearing bosses,sleeve retainers for preventing the sleeves from falling off outward inan axial direction thereof are provided between the sleeves and thefirst and second bearing bosses, and a seal device for preventinglubricating oil in the differential case from flowing out of spacesbetween the side gears and the sleeves are provided between the sidegears and the sleeves.

According to the first aspect of the present invention, the ease ofassembly of the differential device is good, and, even when the driveshafts are removed from the differential device, lubricating oil in thetransmission case and the differential case does not flow out and goodease of maintenance can be ensured.

In particular, after the sleeves are inserted into the differential casethrough the work window, the sleeve retainers can be established at thesame time as the sleeves are fitted and inserted into the first andsecond bearing bosses. Moreover, when the differential gear mechanism isincorporated into the differential case, the sleeves are automaticallyclamped between the sleeve retainers and the side gears. Accordingly,axial movements of the sleeves can be restricted by a simple structure.This structure can contribute to an improvement in ease of assembly.

According to a second aspect of the present invention, in addition tothe first aspect, the sleeves have outside diameters smaller than aninside diameter of the work window and have lengths shorter than aninside diameter of the differential case.

According to the second aspect of the present invention, the sleeves caneasily be fitted and inserted to the inner peripheries of the first andsecond bearing bosses by freely changing orientations of the sleevesinserted into the differential case through the work window within thedifferential case. Thus, ease of assembly can be improved.

According to a third aspect of the present invention, in addition to anyone of the first and second aspects, the sleeve retainers compriseannular inward-facing step portions formed on inner peripheries of thefirst and second bearing bosses, and annular outward-facing stepportions formed on outer peripheries of the sleeves to come in contactwith the inward-facing step portions.

According to the third aspect of the present invention, the sleeveretainers with a simple structure can be configured. This can contributeto cost reduction.

According to a fourth aspect of the present invention, in addition toany one of the first and second aspects, the seal device comprises sealmembers set in fitting portions between the side gears and the sleeves.Note that the seal members correspond to O-rings 26, 32 in embodimentsof the present invention.

According to the fourth aspect of the present invention, the seal devicewith a simple structure can be configured. This can contribute to costreduction.

According to a fifth aspect of the present invention, there is provideda method of assembling the differential device according to the firstaspect, comprising: a first step of passing the sleeves through the workwindow and the inside of the differential case and fitting and insertingthe sleeves to the inner peripheries of the first and second bearingbosses to establish the sleeve retainers; and a second step of, afterthe first step, incorporating the differential gear mechanism into thedifferential case through the work window to establish connectionbetween the side gears and the sleeves.

According to the fifth aspect of the present invention, the differentialdevice can easily be assembled.

The above and other objects, characteristics and advantages of thepresent invention will be clear from detailed descriptions of thepreferred embodiments which will be provided below while referring tothe attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional elevation view of a differentialdevice according to a first embodiment of the present invention.

FIG. 2 is an elevation view of a differential case of theabove-described differential device.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a longitudinal sectional view of a differential deviceaccording to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be describedbased on the accompanying drawings.

First, a first embodiment of the present invention shown in FIGS. 1 to 3will be described. In FIG. 1, a differential device D is housed in atransmission case 1 of an automobile. This differential device Dincludes an integrated differential case 2 and a differential gearmechanism 3 housed in this differential case 2. On a right side portionand a left side portion of the differential case 2, a first bearing boss4 and a second bearing boss 5 aligned on a same axis X are formedintegrally therewith. These first and second bearing bosses 4, 5 aresupported by the transmission case 1 via bearings 6, 6′.

The differential gear mechanism 3 includes a pinion shaft 9 held by thedifferential case 2 to pass through a center C of the differential case2 while being orthogonal to the axis X, a pair of pinion gears 10supported by the pinion shaft 9, a pair of side gears 11 meshing withthe pinion gears 10, and a pair of sleeves 20 connected to hubs 11 a ofthe side gears 11 and rotatably supported by the first and secondbearing bosses 4, 5, respectively. A back face of each gear is rotatablysupported by a spherical inner surface of the differential case 2.Helical lubrication grooves 21 are formed in inner peripheral surfacesof the first and second bearing bosses 4, 5.

The pinion shaft 9 is held by a pair of supporting holes 12 in an outerperipheral portion of the differential case 2. The outer peripheralportion of the differential case 2 is provided with a pin hole 13laterally passing through the outer peripheral portion to be orthogonalto one of the supporting holes 12. A falling-off prevention pin 14press-fitted into the pin hole 13 passes through the pinion shaft 9.This achieves prevention of the falling off of the pinion shaft 9 fromthe supporting holes 12.

Moreover, the differential case 2 has an annular flange 15 formedintegrally therewith on an intermediate portion which is offset from thecenter C of the differential case 2 toward the second bearing boss 5side. A ring gear 17 meshing with an output gear 16 of a gearbox isfastened to the flange 15 with a bolt 22.

As shown in FIGS. 2 and 3, in portions of a peripheral wall of thedifferential case 2 which face each other on a diametral line orthogonalto the axis X, a pair of work windows 18 for machining the sphericalinner surface of the differential case 2 and for facilitating insertionof the differential gear mechanism 3 into the differential case 2 areprovided.

The sleeves 20 are also inserted into the differential case 2 throughthe work windows 18 and fitted and inserted to inner peripheries of thecorresponding bearing bosses 4, 5. To enable such assembly, the sleeves20 have outside diameters smaller than inside diameters of the workwindows 18, and have lengths shorter than an inside diameter of an innerperipheral surface of the differential case 2.

Referring again to FIG. 1, sleeve retainers 24 for preventing thesleeves 20 from falling off outward in an axial direction thereof areprovided between the pair of sleeves 20 and the first and second bearingbosses 4, 5. The sleeve retainers 24 include annular inward-facing stepportions 24 a formed on inner peripheries of the first and secondbearing bosses 4, 5, and annular outward-facing step portions 24 bformed on outer peripheries of the sleeves 20 to come in contact withthe above-described inward-facing step portions 24 a.

Moreover, the sleeves 20 are configured such that outer end portionsthereof protrude from the corresponding bearing bosses 4, 5 outward, andoil seals 25 are interposed between the outer end portions and thetransmission case 1, respectively.

The hub 11 a of the side gear 11 is formed in a shape of a bottomedcylinder having a bottom portion 11 a ₁ facing toward the pinion shaft 9and having a tip end portion 11 a ₂ protruding from a back face of theside gear 11. The tip end portion 11 a ₂ of the hub 11 a is fitted to anannular recessed portion 20 a formed on an inner periphery of an innerend portion of the sleeve 20 via an O-ring 26. The O-ring 26 is attachedto an annular seal groove 27 formed in an outer periphery of the tip endportion 11 a ₂ of the hub 11 a.

Moreover, a back face portion of the side gear 11 and the inner endportion of the corresponding sleeve 20 are connected in a direction ofrotation via a spline 28.

Left and right drive shafts 7, 8 respectively connected to unillustratedleft and right axles pass through the sleeves 20 and are fitted to innerperipheries of the hubs 11 a of the side gears 11 via splines 29.

Next, operations of this embodiment will be described. When thedifferential device D is assembled, as shown in FIG. 3, each of the leftand right sleeves 20 is first inserted into the differential case 2through the work window 18 and then turned inside the differential case2 to be fitted and inserted to the inner periphery of the first bearingboss 4 or the second bearing boss 5, and the outward-facing step portion24 b of the sleeve 20 is brought into contact with the inward-facingstep portion 24 a of the corresponding bearing boss 4 or 5.Subsequently, the side gears 11 and the pinion gears 10 are sequentiallyincorporated into the differential case 2 through the work window 18.The tip end portions 11 a ₂ of the hubs 11 a of the side gears 11 arefitted to the annular recessed portions 20 a of the correspondingsleeves 20, and the O-rings 26 attached to the seal grooves 27 arebrought into tight contact with the inner peripheral surfaces of theannular recessed portions 20 a. Moreover, the back face portions of theside gears 11 are connected to the inner end portions of the sleeves 20via the splines 28. Finally, the pinion shaft 9 for supporting thepinion gears 10 is fitted and inserted into the supporting holes 12 ofthe differential case 2, and the falling-off prevention pin 14 ispress-fitted into the differential case 2 and the pinion shaft 9.

In this way, the sleeves 20 are inserted into the differential case 2through the work window 18 and then fitted and inserted into the firstand second bearing bosses 4, 5, and, at the same time, contacts betweenthe inward-facing step portions 24 a and the outward-facing stepportions 24 b of the sleeve retainers 24 are achieved. Accordingly, goodease of assembly can be obtained. Also, when the differential gearmechanism 3 is incorporated into the differential case 2, the sleeves 20are automatically clamped between the inward-facing step portions 24 aof the first and second bearing bosses 4, 5 and the side gears 11.Accordingly, axial movements of the sleeves 20 can be restricted by asimple structure.

The differential device D assembled as described above is incorporatedinto the transmission case 1, and oil seals 25 are set between the outerend portions of the sleeves 20 and the transmission case 1. Then,lubricating oil is injected into the transmission case 1. At this time,part of the lubricating oil flows into the differential case 2 throughthe work windows 18 to be used for lubrication between various portionsof the differential gear mechanism 3.

Thus, the lubricating oil in the transmission case 1 is prevented fromflowing out of the outer peripheries of the outer end portions of thesleeves 20 by the oil seals 25, and the lubricating oil in thedifferential case 2 is prevented from flowing out of fitting portions Fbetween the side gears 11 and the sleeves 20 by the O-rings 26. Thismeans that the lubricating oil in the transmission case 1 and thedifferential case 2 does not flow out even when the drive shafts 7, 8are removed from the side gears 11.

After the transmission case 1 housing the differential device D ismounted on the automobile, the left and right drive shafts 7, 8 arefitted to the inner peripheries of the hubs 11 a of the correspondingside gears 11 via the splines 29.

When the differential device D is activated, rotating torque from theside gears 11 is transmitted to the drive shafts 7, 8 via the splines29. At the same time, rotation of the side gears 11 is transmitted tothe sleeves 20 via the splines 28. Accordingly, the side gears 11, thedrive shafts 7, 8, and the sleeves 20 integrally rotate. At this time,the outer peripheral surfaces of the sleeves 20 are lubricated with thelubricating oil held in the lubrication grooves 21 of the first andsecond bearing bosses 4, 5.

Next, a second embodiment of the present invention shown in FIG. 4 willbe described.

In this second embodiment, short shafts 30 are integrally provided onthe back faces of the side gears 11 in a protruding manner instead ofthe hubs 11 a, and the short shafts 30 are fitted to the innerperipheries of the sleeves 20 via splines 31. Further, the drive shafts7, 8 are fitted into the sleeves 20 via splines 34. Accordingly,rotating torque from the side gears 11 is transmitted to the driveshafts 7, 8 via the sleeves 20. The drive shafts do no pass through theside gear axially. Moreover, an annular seal groove 33 is provided onone of end surfaces of the side gear 11 and the sleeve 20 which faceeach other, and an O-ring 32 which comes in tight contact with the otherend surface is attached to the seal groove 33. Except for theabove-described points, the configuration of this embodiment issubstantially the same as that of the previous embodiment. Accordingly,portions corresponding to those of the previous embodiment are denotedby the same reference numerals in FIG. 4, and explanations which havealready been made in the previous embodiment will be omitted.

This second embodiment can also achieve effects similar to those of theprevious embodiment.

The present invention is not limited to the above-described embodiments,but various design changes can be made without departing from the gistthereof. For example, in the above-described embodiments, the fasteningof the ring gear 17 and the flange 15 with bolts may be replaced byjoining by welding. Moreover, the annular sleeve retainers 24 may bereplaced by sleeve retainers in which the sleeves 20 partially engagewith the bearing bosses 4, 5 in the peripheral direction so as not tofall off. Further, the shape of the inner peripheral surface of thedifferential case 2 may be a box shape, a cylindrical shape, or the likeinstead of a spherical shape. In any of these cases, the sleeves 20 needto be configured to be capable of being passed through the inside of thedifferential case 2 and fitted and inserted to the inner peripheries ofthe bearing bosses 4, 5. Moreover, to prevent the lubricating oil in thedifferential case 2 from flowing out into the hubs 11 a of the sidegears 11, plugs may be press-fitted to the inner peripheries of the hubs11 a in a liquid tight manner instead of the bottom portions 11 a ₁ ofthe hubs 11 a. Furthermore, the lengths of the left and right sleeves 20may differ from each other.

What is claimed is:
 1. A differential device comprising: a differentialgear mechanism; and an integrated differential case which houses thedifferential gear mechanism, wherein the differential case includes:first and second bearing bosses formed integrally on one side portionand an other side portion of the differential case and aligned on a sameaxis to be rotatably supported by a transmission case; and a work windowfor inserting the differential gear mechanism, the work window beingprovided in a peripheral wall of the differential case, a pair of shaftportions are respectively formed integrally with a pair of left andright side gears of the differential gear mechanism, the shaft portionsrespectively extend outward in an axial direction from back faces of theside gears, a pair of sleeves extend outside of the differential casethrough the first and second bearing bosses, the sleeves have innerperipheral surfaces thereof respectively fitted on the shaft portions,left and right drive shafts are respectively connected to the pair ofside gears or the pair of sleeves, and out of the pair of shaft portionsand the pair of sleeves, only the pair of sleeves are rotatably fittedand supported respectively on inner peripheral surfaces of the first andsecond bearing bosses.